D-xylose is a monosaccharide used to measure small intestinal absorption. Little is known on the effect of co-administration of food with its associated delay in gastric emptying rate on D-xylose absorption. In the current study, 8 volunteers and 12 patients with gastroparesis will receive D-xylose IV, in oral solution and mixed with oatmeal on 3 separate occasions with interval serum sampling. The parameters of gastric emptying will be determined with a gastric emptying scan using oatmeal. Comparison of D-xylose concentration VRS time curves will be made using model dependent pharmacokinetics with the SAAMII and Cousaam programs.